KR100376247B1 - Producing method for nano-size ultra fine Titanium Dioxide by the chemical reaction using flame - Google Patents

Abstract

The present invention relates to a method for preparing nano-size titanium dioxide (TiO ₂ ) ultrafine powder by vapor phase oxidation of titanium tetrachloride (TiCl ₄ ) using a flame in a method of preparing ultrafine powder.

In the case of preparing nano-sized ultrafine powders by gas phase chemical reaction, the concentration of the sample in the reaction gas must be kept very low. Therefore, in order to increase the production of nano-sized powder per unit time, a large amount of gas reacts with the increase of the reactant injection amount. In the present invention, the nano-size TiO ₂ ultrafine powder is prepared from TiCl ₄ by using a reaction system such as TiCl ₄ -argon-hydrogen-oxygen-air using a diffusion flame reactor composed of a five-pipe. It is characterized by increasing the production of nano-size powder per unit time so that less unreacted material is present and the combustion gas can be completely burned.

Description

Producing method for nano-size ultra fine Titanium Dioxide by the chemical reaction using flame}

The present invention relates to a method for preparing nano-size titanium dioxide (TiO ₂ ) ultrafine powder by vapor phase oxidation of titanium tetrachloride (TiCl ₄ ) using a flame in a method of preparing ultrafine powder.

Nano-size ultra fine powder generally refers to a powder having a particle size of 50 nm or less, and is widely used as a new material due to the high specific surface area and high activity of sugar per unit weight.

Nano-size titanium dioxide ultrafine powder is used as a high-quality pigment and photocatalyst, and is also used as a coating material for cosmetics, drugs and transparent soundproof panels using the same because of its excellent UV-blocking properties.

The nano-size titanium dioxide (hereinafter referred to as "TiO ₂ ") ultrafine powder production method includes a physical method of producing ultrafine powders by heating and evaporating a metal, condensing the metal vapor, and a chemical method of preparing a metal compound by chemical reaction. Is being used.

The process for producing nano-size TiO ₂ ultrafine powder by the above physical method requires a lot of energy to evaporate the metal, which has the advantage of producing high purity powders with high production cost and low productivity. Chemical method has lower purity than physical method but low manufacturing cost and high productivity. Among chemical methods, gas phase method and liquid phase method are used.

Hereinafter, a manufacturing method of the nano-size TiO ₂ ultrafine powder by the vapor phase method among the chemical methods related to the present invention among the above-described manufacturing methods will be described.

When preparing nano-size TiO ₂ ultra fine powder by the gas phase chemical reaction method, a high temperature and gas flow rate of 1000 ° C. or higher is required. For this purpose, a technique of forming reaction conditions in the gas phase while maintaining a high temperature using a flame is employed. Known, the temperature of the flame, the gas flow rate, the concentration of the reactants, the additives, etc. in the production of ultra-fine powders are important reaction variables that control the size and crystalline form of the primary particles.

Known techniques for the preparation of powders by gas phase chemical reactions using flames include US Pat. No. 5,698,177 (named Process for producing ceramic powders, especially titanium dioxide useful as a photocatalyst, filed June 8, 1995) and US. 5,861,132 (named Vapor phase flame process for making ceramic particles using a corona discharge electric field, filed September 4, 1997).

U.S. Patent No. 5,698,177 discloses a corona electric field formed on the top of the reactor burner by controlling reaction parameters, injecting additives and forming a reactor for the production of TiO ₂ powder for photocatalysts in a reaction system consisting of TiCl ₄ -air-hydrocarbon-based combustion gases. Various methods are proposed for the effect of TiO ₂ powder by the reaction of TiCl ₄ and oxygen in the gas phase, and flame reactor, sample injection method, sample injection amount, air injection amount, electric field voltage And amounts of additives and the like.

In addition, the US patent US 5,861,132 forms a corona electric field on the top of the reactor, and uses various flame reactors (pre-mixed flame reactor, turbulent flame reactor, larminar diffusion flame reactor) to use various metal oxides (silica dioxide, including silica). , Alumina, zirconia, and the like) are disclosed.

In the case of preparing nano-sized ultrafine powders by gas phase chemical reaction, the concentration of the sample in the reaction gas should be kept very low. Therefore, in order to increase the production of nano-sized powder per unit time, a large amount of gas together with the increase of the reactant injection amount It must be injected into the reaction zone (flame).

However, in the TiCl ₄ -air-hydrocarbon-based combustion gas reaction system introduced into the triple tube proposed in US Pat. No. 5,698,177, a large amount of air and combustion gas are injected into the air, thereby increasing the linear velocity in the burner. There are problems such as the presence of unreacted substances and incomplete combustion of the combustion gas due to the reduction of residence time.

In the present invention, in order to solve the problems of the prior art, using a diffusion flame reactor composed of a five-pipe TiCl ₄ -argon-hydrogen-oxygen-air, TiCl ₄ -argon-hydrogen-air-air and TiCl ₄ -argon- In preparing nano-size TiO ₂ ultrafine powder from TiCl ₄ using a hydrogen-oxygen / air-air reaction system, it is possible to keep the sample concentration in the reaction gas low, to make less unreacted substances, and to burn the combustion gas completely. There is a technical challenge to increase the production of nano-size powder per unit time.

1 is a schematic view of the ultra-fine powder production apparatus used in the present invention

2 is an electron micrograph of the TiO ₂ ultra fine powder produced according to the change in the concentration of TiCl _{4 in} the reaction gas

Figure 3 is the crystallographic result of the TiO ₂ ultra fine powder produced according to the change of oxygen flow rate

4 is the average particle size and crystalline change of the TiO ₂ ultra fine powder produced according to the hydrogen flow rate control

※ Explanation of code about main part of drawing ※

10: sample evaporation unit 11: evaporation vessel

12 syringe pump 13: evaporator

14,15,16,17,18: Halls 1 to 5

30: particle collecting unit

The technical task of the present invention described above is to vaporize the liquid reactant TiCl ₄ to vaporize TiCl ₄ vapor-argon-hydrogen-oxygen-air, TiCl ₄ vapor-argon-hydrogen-air-air and TiCl ₄ vapor-argon-hydrogen Composed of oxygen / air-air, the above gaseous mixed gas can be passed through a high temperature flame during combustion to produce nanosize TiO ₂ ultra fine powder by oxidation, and the concentration of TiCl _{4 in} the reaction gas, Since gas flow rate, gas composition, etc. are the main variables, it is possible to achieve the technical task of the present invention by varying these parameters to have an optimal particle size and crystal form.

Hereinafter, a method of preparing TiO ₂ ultrafine powder by controlling the amount of TiCl ₄ vapor, hydrogen, oxygen, air, and argon injected into a flame reactor in preparing nanosize TiO ₂ ultrafine powder will be described in detail with reference to the accompanying drawings. .

Figure 1 schematically shows a manufacturing apparatus used in the manufacturing method of the present invention, vaporizing liquid TiCl ₄ as a reactant in the sample evaporation unit 10, and generates a flame with a burner 20 consisting of a five-pipe When the vaporized TiCl ₄ is passed through a flame, nanosize titanium dioxide ultrafine powder is formed by an oxidation reaction. The produced titanium dioxide ultrafine powder is collected in the particle collecting unit 30 to recover the TiO ₂ ultrafine powder.

<Example 1>

This embodiment is intended to control the particle size of the powder produced by changing the concentration of TiCl _{4 in} the gas during the production of TiO ₂ ultra fine powder.

TiCl ₄ (99.9%), which is a liquid sample, was injected into the evaporation vessel 11 of the evaporator 10 shown in FIG. 1 by a syringe pump 12, and then the temperature of the evaporator 13 was 180 ° C. After the vaporization and vaporization to the first gas pipe (14) located in the center of the burner 20 together with the argon gas, which is a transfer gas, argon, hydrogen, oxygen and air is the fifth pipe (15, 16, 17, 18 in the order of injection into the diffusion burner 20 at the same speed as in Table 1 below to generate a flame.

The concentration of TiCl ₄ in the gas injected into the diffusion burner 20 was adjusted in the range of 1.13x10 ^{-5 to} 4.44x10 ^-5 mol / l, and the flow rate of each gas injected into the burner of the five-pipe was stable flame. After confirming the conditions to maintain the state with the naked eye, it was dispensed and injected as shown in the experimental conditions shown in Table 1.

division gas Flow rate (ℓ / min) Article 1 Argon and weather TiCl ₄ 2 Article 2 Algon 5 Article 3 Hydrogen 6 Article 4 Oxygen 15 Article 5 air 60

The temperature of the flame formed was measured by thermocouples and the temperature was maintained at about 850 ℃ at the center of the burner and showed the highest temperature (1700 ℃) at 7mm in the radial direction from the center.

The concentration of TiCl ₄ in the reaction gas was varied under the combustion conditions of Table 1, and the particle size change and crystal form produced were investigated. The average size of the particles produced was assumed to be spherical particles with no pores per unit weight. The specific surface area of the particles was obtained from the BET analysis results using the conversion equation (d _p = 6 / (ρ _p · A), where ρ _p is the density of TiO ₂ (g / cm ³ ) and A is Specific surface area (m ² / g)).

As a result of calculating the average particle size change of the TiO ₂ fine powder by the conversion equation, it increased from 19 nm to 28 nm with increasing sample concentration.

Figure 2 is an electron micrograph of the nano-size TiO ₂ ultra fine powder prepared by the above method (TiCl ₄ initial concentration: (a) 1.13x10 ^-5 , (b) 2.27x10 ^-5 , (c) 3.45x10 ^-5 , (d) 4.54x10 ^-5 mol / l), the size of the particles produced was found to be almost the same as that obtained from the BET analysis, and it was found to increase with increasing concentration of reactants. As a result of XRD analysis to investigate the crystalline form of the powder, powder containing about 45% of anatase type was prepared under the conditions tested in this study.

<Example 2>

In this embodiment, the TiO ₂ powder manufacturing experiment was performed by reducing the flow rate of oxygen injected into the reactor to reduce the temperature of the flame, and the experimental conditions were the oxygen flow into the fourth tube 17 under the gas injection conditions shown in Table 1. After reducing the flow rate from 15 to 10, 5 (l / min), the total flow rate was kept constant by increasing the flow rate of the air injected into the fifth tube 18, which kept the concentration of TiCl ₄ in the gas constant (2.27). x 10 ^-5 mol / l), the maximum temperature of the flame decreased from 1700 to 1400 ° C.

As a result of the TiO ₂ powder production experiment under the above conditions, the change of the average particle size of the TiO ₂ fine powder decreased from 23 nm to 14 nm as the oxygen flow rate was decreased. This is because the lower the growth rate of the particles due to the aggregation.

The result of crystalline analysis of the TiO ₂ powder produced by the above method is shown in FIG. 3 (Oxygen flow rate: (a) 15, (b) 10, (c) 5 (l / min)), and the results of FIG. It can be seen that there is no significant change when the oxygen flow rate is reduced to 10 ℓ / min, but the content of anatase increases rapidly as the oxygen flow rate is reduced to 5 ℓ / min.

The anatase content was 41, 45 and 80% as the flow rate of oxygen decreased as described above.

<Example 3>

In this embodiment, the flow rate of hydrogen injected into the reactor under constant reaction conditions was varied from 4 to 8 l / min, and TiO ₂ powder was prepared to analyze the size and crystal form of the particles produced.

Experimental conditions maintained the concentration of TiCl _{4 in} the gas to 2.27x10 ^-5 mol / l, and the gas injection amount excluding hydrogen was 5 l / min for argon (second tube (15)) and air (fourth tube (17)). 10 L / min and air (5th tube 18) were maintained at 65 L / min.

In the present embodiment, the gas injected into the fourth pipe 17 of the burner is replaced with oxygen from air. This is to minimize the amount of oxygen, and the maximum temperature is obtained by measuring the temperature of the flame formed according to the change of the hydrogen flow rate. Was observed to vary from 1,300 to 1,000 ° C.

As a result of the TiO ₂ powder manufacturing experiments under the above conditions, the average particle size decreased from 29 to 12 nm as the flow rate of hydrogen decreased from 8 to 4 l / min. It was.

In addition, as the hydrogen flow rate decreased from 8 to 4 L / min, the change in the crystal form of the TiO ₂ powder produced increased the anatase content from 27 to 75% (FIG. 4).

Example 4

In this embodiment, TiO ₂ powder was prepared by mixing air with oxygen gas injected into the fourth tube 17 under the conditions of Example 2, wherein the experimental conditions were the same concentration and total flow rate of TiCl ₄ as in Example 2. While maintaining the flow rate, the flow rate of hydrogen in the third pipe 16 was introduced at 5 L / min, and the fourth pipe 17 was injected by mixing 4 L / min of oxygen and 6 L / min of air.

At this time, the TiO ₂ powder produced had an average particle size of 15 nm and a crystalline form of anatase content of 77%. The above-described examples were performed by increasing or decreasing the flow rate of each gas introduced into the fold pipe, and the scope of the present invention is The present invention is not limited to these embodiments, and the flow rates of TiCl ₄ and each gas introduced into each inlet pipe can be modified by those skilled in the art to which the present invention belongs. Modified implementation without departing from the identity of the will not depart from the scope of the invention.

In the present invention, using a flame and using a reactor composed of five tubes in preparing nano-size titanium dioxide ultrafine powder by gas phase chemical reaction, TiCl ₄ -argon-hydrogen-oxygen-air, TiCl ₄ -argon-hydrogen-air- It has the effect of providing a technique for producing TiO ₂ ultra fine powder in a reaction system of air and TiCl ₄ -argon-hydrogen-oxygen / air-air and from this, providing data of reactor design for mass production.

Claims (7)

In the method for producing nano-size titanium dioxide ultrafine powder by a gas phase reaction using a flame, a titanium tetrachloride (TiCl ₄ ) vapor is injected into a flame reactor consisting of a five-pipe and the initial concentration of the flame is 1.13x10 ^-5. ~ 4.54x10 ^-5 (mol / l), where the flow rate of steam is introduced into two parts of the total gas, argon gas is introduced into six parts into the second pipe, and hydrogen gas is introduced into the third pipe. The fourth pipe allows oxygen gas to flow into 17 parts, and the fifth pipe simultaneously introduces air into 68 parts to produce flames above 1,000 ° C. At this time, titanium tetrachloride vapor is oxidized in the gas phase. Reaction to produce nano-size titanium dioxide ultrafine powder by vapor-chemical reaction, characterized in that to produce a nano-size titanium dioxide ultrafine powder having an average particle size of 50 nanometer or less Law. delete The method of claim 1, wherein nitrogen gas at the same flow rate is introduced into the second tube of the gas introduced into the flame reactor. delete According to claim 1, wherein the flow rate of the oxygen gas flowing into the fourth pipe of the composition of the gas flowing into the flame reactor from 17 to 6 parts of the total flow rate and the air flow into the fifth pipe by the reduced flow rate Nano-size titanium dioxide ultra-fine powder production method by a gas phase chemical reaction, characterized by increasing the flow rate of. The method of claim 1, wherein the oxygen gas introduced into the fourth pipe of the composition of the gas flowing into the flame reactor is replaced with air of the same flow rate and the flow rate of hydrogen gas flowing into the third pipe is 9 to 4 parts of the total flow rate. A method for producing nano-size titanium dioxide fine powder by vapor phase chemical reaction, characterized by changing the flow rate and increasing and decreasing the flow rate of the air flowing into the fifth pipe by the increased and decreased flow rate. According to claim 3, the composition of the gas flowing into the flame reactor flows into the third pipe by mixing oxygen gas (4 parts of the total flow rate) and air flow rate (7 parts of the total flow rate) to the fourth tube and A method for producing nano-size titanium dioxide fine powder by vapor phase chemical reaction, characterized by increasing the flow rate of air flowing into the fifth pipe by reducing the flow rate of hydrogen gas into 6 parts of the total flow rate.